Distribution method and flexible manufacturing apparatus

ABSTRACT

A plurality of machine tools are disposed along a circulating conveyor transporting materials to be processed by the machine tools, and material selector subsystems associated with the respective machine tools are provided together with a load/unload command subsystem. The material selector subsystems exchange information therebetween to track materials loaded on the conveyor under command of the load/unload command subsystem so as to reserve materials requested by the individual machine tools. Each of the reserved materials is unloaded from the conveyor under command of the load/unload command subsystem as soon as it arrives at the position of the corresponding machine tool.

.Iadd.This application is a continuation of U.S. application Ser. No.143,960, filed Dec. 22, 1989, now abandoned, which is a reissue of U.S.application Ser. No. 547,133, now U.S. Pat. No. 4,564,102. .Iaddend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for transportation ofmaterials, in which materials to be machined by individual machine toolsare continuously circulated on a conveyor, and a specific one selectedfrom among them is unloaded from the conveyor to be supplied to aspecific machine tool when the specific material is requested by thespecific machine tool.

2. Description of the Prior Art

Hitherto, materials to be machined by individual machine tools accordingto the production schedule have been previously distributed tocorresponding ones of the machine tools, or such materials have beenstored in a warehouse so that a specific one selected from them can besupplied by a conveyor from the warehouse to a specific machine toolupon request for machining by the machine tool. However, the formermethod is not applicable to a production system in which the productionschedule is frequently changed resulting in a corresponding change ofthe machine tools participating in material processing or the productionschedule cannot be sufficiently laid out in advance. According to thelatter method, on the other hand, pallets on which the materials arecarried, respectively, are marked by a central unit according to theproduction schedule with the addresses of specific machine tools whichare scheduled to process the materials and the pallets are transportedby the conveyor. Thus, in the case of the latter method, therelationship between the machine tools and the materials to be processedthereby must be preliminarily determined. Further, an addressing errorof the central unit results in maloperation of the whole system.Further, it has been required for the central unit to collect andprocess a vast amount of information, since the central unit must alwaysexactly grasp the operating state and occurrence of operational failure,if any, of the individual machine tools. Furthermore, the latter method,in which a material is not transported to a machine tool by the conveyoruntil the machine tool requests distribution of such a material, hasbeen defective in that a considerably long period of time is requireduntil the material is actually supplied to the machine tool after therequest is issued.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a method andapparatus for transportation of materials, which can easily deal with achange of the production schedule, operational failure of a machine tooland maintenance required for the machine tools, and in which any errorof material selection does not result in mal-operation of the wholesystem.

The present invention which attains the above object is featured by thefact that materials required for production are placed on a circulatingconveyor to be continuously circulated past a plurality of machine toolsso that materials requested by the individual machine tools can bereadily selected from among those circulated to the positions of themachine tools, and material selector subsystems belonging or connectedto the machine tools respectively exchange information therebetween totrack the materials being circulated so that a requested material can bereadily reserved and then unloaded from the conveyor upon arrival at theposition of the machine tool scheduled for machining it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the general structure of a preferredembodiment of the system according to the present invention.

FIG. 2 is a diagrammatic elevation view showing the arrangement ofpallets and materials on the conveyor shown in FIG. 1.

FIG. 3 is a block diagram showing the structure of one form of one ofthe material selector subsystems shown in FIG. 1.

FIG. 4 is a block diagram showing the structure of one form of thematerial selector controller shown in FIG. 3.

FIG. 5 shows data stored in one form of the material tracking file shownin FIG. 4.

FIG. 6 shows data stored in one form of the requested material data fileshown in FIG. 4.

FIGS. 7 to 12 are flow charts illustrating the operation of the materialselector subsystem shown in FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the general structure of a preferred embodiment of thesystem according to the present invention.

Referring to FIG. 1, a material transporting conveyor 2 is circulatedcontinuously in a direction shown by an arrow past a plurality ofdistributed machine tool subsystems 11 to 15 and a load/unload commandsubsystem 16. Material selector subsystems 31 to 35 and 36 are connectedto the machine tool subsystems 11 to 15 and the load/unload commandsubsystem 16 respectively so as to load and unload in a well-knownmanner selected materials on and from the conveyor 2. These materialselector subsystems 31 to 36 are interconnected by an informationtransmission loop 4 for exchange of information of materials on theconveyor 2 and information of their positions on the conveyor 2.

FIG. 2 shows, for example, that each of materials A, B, C, and so on iscarried on one of the pallets 61 to 6n which are loaded on the conveyor2 and no materials is carried on a pallet 62.

The load/unload command subsystem 16 applies a command to the materialselector subsystem 36 for loading newly externally supplied materialsfrom the warehouse on the conveyor 2 or unloading materials from theconveyor 2 for storing the materials to the warehouse.

FIG. 3 shows the internal structure of one form of the material selectorsubsystem 31. The subsystems 32 to 35 are arranged in the same manner asthe subsystem 31.

Referring to FIG. 3, the material selector subsystem 31 includes a pairof material detectors 71 and 72 for detecting a pallet on the conveyor2, a pallet detector 73 receiving the output signals from the detectors71 and 72, a material selector 74 for selectively loading or unloadingmaterials to or from the conveyor 2, a material selector controller 75for controlling the material selector 74, and an informationtransmission controller 76 for controlling exchange of informationbetween the material selector subsystem 31 and the other materialselector subsystems.

FIG. 4 shows the internal structure of one form of the material selectorcontroller 75 shown in FIG. 3. Referring to FIG. 4, the materialselector controller 75 includes a processor 80, an interface 81connected to the pallet detector 73, an interface 82 connected to theinformation transmission controller 76, an input/output buffer 83, amaterial tracking file 84, a requested material data file 85, a palletmonitoring timer 86, a material request monitoring timer 87, and aninterface 88 connected to the machine tool subsystem 11.

FIGS. 5 and 6 show data stored in the material tracking file 84 andrequested material data file 85 respectively, by way of example.

FIGS. 7 to 12 are flow charts illustrating by way of example, the stepsof processing by the processor 80 shown in FIG. 4.

The operation of the material selector subsystem 31 shown in FIGS. 3 and4 will now be described with reference to FIGS. 5 to 12.

The data of a material requested for a workpiece that can be processednow is broadcast from the machine tool subsystem 11 to the materialselector controller 75 (block 101 in FIG. 7). The material selectorcontroller 75 stores the data of requested material once in theinput/output buffer 83. If the data in the buffer 83 is the data ofrequested material, the data is transferred into the requested materialdata file 85 (block 102 in FIG. 7).

On the other hand, when passage of a pallet is detected by the materialdetector 71 (block 109 in FIG. 8), the data of the material on thedetected pallet is transmitted from the information transmissioncontroller 76 to the downstream material selector subsystems by way ofthe information transmission loop 4. In the material selector controller75 in each of the downstream material selector subsystems, the data ofthe material, transmitted thereto from the upstream material selectorsubsystem through the information transmission loop 4, informationtransmission controller 76 and interface 82, is stored once in theinput/output buffer 83 and then stored in the material tracking file 84(blocks 110 and 111 in FIG. 8). In this manner, data of materials aretransmitted sequentially from the upstream material selector subsystemto be stored in the material tracking file 84 in each of the downstreammaterial selector subsystems, and, at the same time, the data of thematerials on the pallets departing toward the downstream materialselector subsystems from the position of the material detector 72 ineach of the material selector subsystems are erased from the materialtracking file 84. Thus, in the downstream material selector subsystemnext adjacent to the directly upstream material selector subsystem, thedata of the materials on the pallets 61 to 63 are stored in the materialtracking file 84 in a sequential order as shown in FIG. 5. FIG. 5 showsthat each pallet data is composed of a material name data and a statusdata, and the status data designated by the symbol R₁ indicates that thematerial B is reserved for the material selector subsystem 31.

When the data of the requested material stored in the requested materialdata file 85 is also stored in the material tracking file 84 as shown inFIG. 5 (block 103 in FIG. 7) and when arrival of the pallet carrying therequested material is detected by the material detector 71 (block 109 inFIG. 8), and, then, when the material selector controller 75 is informedof the lapse of a predetermined period of time after detection of thepallet arrival, from the pallet monitoring timer 86 (block 113 in FIG.8), the material selector controller 75 commands the material selector74 to unload the specific material from the position of the pallet onthe conveyor 2 (block 115 in FIG. 8). The above-mentioned predeterminedperiod of time is selected such that the material selector 74 is readyfor unloading the material from the pallet detected by the materialdetector 71 when the predetermined period of time has lapsed after thedetection. The material selector 74 supplies the specific material tothe machine tool subsystem 11. At the same time, the material selectorcontroller 75 erases the data of the unloaded or removed material fromboth of the material tracking file 84 and the requested material datafile 85 (block 116 in FIG. 8).

If the data of the material B stored in the requested material data file85 is not found in the material tracking file 84, the status data of thematerial B in the requested material data file 85 is set at the"waiting" state W, and a flag indicative of the "Waiting" state W isthen set (block 106 in FIG. 7). At the same time, a request for thematerial B is broadcast from the material selector controller 75 by wayof the information transmission loop 4 (block 107 in FIG. 7), and thematerial request monitoring timer 87 is set (block 108 in FIG. 7).

When each of the other material selector subsystems receives the requestfor the material B broadcast from the specific material selectorcontroller 75 and transmitted by way of the information transmissionloop 4 (block 117 in FIG. 9), it searches whether or not the specificmaterial B is included in its material tracking file 85 (block 118 inFIG. 9), and a reservation flag R₁ indicative of reservation of thecorresponding pallet 63 is set when the material B is included in itsmaterial tracking file 84 and is not still reserved (blocks 119 and 120in FIG. 9). Then, the fact that the requested material B is now reservedis broadcast from the material selector controller 75 of that subsystemto the material selector controller 75 having broadcast the request forthe material B (block 121 in FIG. 9). When the requested material B isfound, the material selector controller 75 sets the reservation flag R₁indicative of reservation of the requested material B in the requestedmaterial data file 85.

If two or more of the material selector subsystems answer booking of thereservation of the material B in response to the request for thematerial B, (blocks 129 and 130 in FIG. 11), the material selectorcontroller 75 selects only one of the reserved pallets from among themand broadcasts cancellation of the reservation to the other pallets(block 132 in FIG. 11). When the reservation-cancelled pallet isincluded in the material tracking file 84 in each of the materialselector controller 75 receiving the broadcast informing thecancellation of reservation, the material selector controller 75 resetsthe material reservation flag of the corresponding pallet (blocks 122,123 and 124 in FIG. 10).

When the material selector controller 75 having broadcast the requestfor the material B does not receive the answer informing reservation ofthe request material B from any one of the other subsystems in spite ofthe fact that the material request monitoring timer 87 has timed apredetermined period of time, a request waiting flag W indicative ofwaiting a request for the material B is set in the requested materialdata file 85 (blocks 125, 126, 127 and 128 in FIG. 11). Thereafter, thematerial selector controller 75 broadcasts the request for the materialof waiting state at predetermined constant time intervals. When thebooking of reservation of the material B is answered, the requestwaiting flag W is reset, and the material reservation flag R is set(blocks 129, 130 and 131 in FIG. 11).

When the material B cannot be reserved although the material request hasbeen broadcast more than a predetermined number of times (blocks 133 and134 in FIG. 12), the material selector controller 75 of the subsystem 31displays the impossibility of reservation, and, at the same time,broadcasts it to the other material selector controllers (block 135 inFIG. 12). Upon receiving this broadcast informing the impossibility ofmaterial reservation, the material selector subsystem 36 displays it tooand calls for supply of the specific material to the system from theexternal source.

It will be understood from the foregoing detailed description of thepresent invention that distributed machine tools can select requiredmaterials to meet any machining demand, and the system can deal withoperational failure and recovery of whichever machine tool at whatevertime and can also deal with a system expansion, so that there is no needfor previously arranging the material distribution schedule. Further,the present invention can save the useless length of time requiredhitherto for the transportation of materials to the machine toolswhenever such materials are requested, and can also save the spacerequired for storage of materials.

While the present invention has been described with refernece to itsapplication to a system including a plurality of distributed machinetools by way of example, it is apparent that the present invention isnot in any way limited to application to such a specific system, and isapplicable also to any one of assembling, working and other processingsystems.

We claim:
 1. A method for transporation of materials in awork-processing system including a plurality of work-processing meansprocessing materials transported thereto by transporting means,comprising the steps of loading newly externally supplied materials onsaid transporting means detecting material transported by saidtransporting means by using a detector means associated with each ofsaid work-processing means and storing the results of detection; issuinga material request from any work-processing means when thework-processing means requires a material which is not detected by saidwork-processing means; communicating the material request from thework-processing means which issued the material request to otherprocessing means; causing each of said work-processing means to search arequested material indicated by the material request, based on thestored results of detection while keeping coordination with the otherwork-processing means in response to receipt of the material request;reserving said requested material for the work-processing means whichissued the material request when said material is found on saidtransporting means as a result of the searching step while maintainingthe material request when the searching step cannot find said requestedmaterial on said transporting means; and unloading said reservedmaterial from said transporting means upon arrival of said material atthe position of said work-processing means which issued the materialrequest thereby supplying said material to said work-processing means.2. An apparatus for transportation of materials in a work-processingsystem including a plurality of work-processing means processingmaterials transported thereto by transporting means, comprisingload/unload commanding means for commanding loading of newly externallysupplied materials on said transporting means and commanding unloadingof said materials from said transporting means; transmission controlmeans provided for each of said work-processing means for transmitting amaterial request issued from work-processing means associated therewithto other work-processing means and receiving a material requesttransmitted from the other work-processing means; and material selectormeans provided for each of said work-processing means and comprisingmeans at each work-processing means for storing the material requestissued from the work processing associated therewith and the materialrequests transmitted from the other work-processing means; means at eachwork-processing means for detecting materials on said transporting meansand storing the results of detection, means for searching a requestedmaterial based on the contents of said material request storing meansand said means for storing the results of detection while keepingcoordination among said work-processing means, means for reserving therequested material when it is found by said searching means that therequested material on said transporting means and reporting areservation of requested material to other work-processing means, andmeans for continuously issuing a material request when saidworkprocessing means cannot find the requested material on saidtransporting means.
 3. An apparatus according to claim 2, wherein eachof said work-processing means comprises a first subsystem for carryingout a work process and a second subsystem including said materialselector means and said transmission control means, said transmissioncontrol means being connected through a transmission path to thetransmission control means of the other work-processing means.
 4. Anapparatus according to claim 3, wherein each of said work-processingmeans further comprises means for reporting to the load/unloadcommanding means that requested material is not reserved after repeatedissuance of a material request a predetermined number of times, so as tocause said load/unload commanding means to supply the requestedmaterial. .Iadd.
 5. A method for processing materials in a processingsystem including a plurality of subsystems which process at least oneselected material and operate independently of each other, a means forrelatively moving materials with respect to said subsystems and atransmission medium connected with said subsystems for transmittinginformation relating to the materials to said subsystems, comprising thefollowing steps executed by each of said subsystems:transmittinginformation relating to the materials moved by said moving means to saidtransmission medium; receiving information relating to the materialsmoved by said moving means and transmitted from other subsystems throughsaid transmission medium; selecting at least one necessary material fromamong the materials moved by said moving means based on the receivedinformation relating to the materials from said transmission medium; andprocessing said selected material upon arrival said selected material..Iaddend. .Iadd.6. A method for processing materials according to claim5, which further includes a step of reserving said necessary materialwhen it is selected by said selecting step so as to process saidselected material upon arrival of said reserved material. .Iaddend..Iadd.7. A method for processing materials according to claim 5, whereinsaid moving means comprises a means for transporting said materials, anda means for loading said materials on said transporting means. .Iaddend..Iadd.8. A method for processing materials according to claim 5, whereinsaid information on the materials comprises information showing thepresence of a material which has been moved by said moving means..Iaddend. .Iadd.9. An apparatus for processing materials, comprising;aplurality of first subsystems each of which processes at least oneselected material; means for relatively moving the materials withrespect to said subsystems; a plurality of second subsystems associatedwith said first subsystems, respectively, and connected to atransmission medium, each of said second subsystems configured tooperate independently of each other based on information on saidtransmission medium and including means for transmitting informationrelating to the materials moved by said moving means to saidtransmission medium; and means for selecting at least one necessarymaterial from among the materials moved by said moving means based onthe information relating to the materials transmitted from othersubsystems and received from said transmission medium, and each of saidfirst subsystems including means responsive to selection of at least onenecessary material by the associated second subsystem for processingsaid selected material upon arrival thereof. .Iaddend. .Iadd.10. Anapparatus for processing materials according to claim 9, furtherincluding means for reserving said necessary material when it isselected by said selecting means so as to process said selected materialupon arrival of said reserved material. .Iaddend. .Iadd.11. An apparatusfor processing materials according to claim 9, wherein said moving meanscomprises means for transporting said materials. .Iaddend. .Iadd.12. Anapparatus for processing materials according to claim 9, wherein saidinformation on the materials comprises information showing the presenceof a material which has been moved by said moving means. .Iaddend..Iadd.13. A method for transportation of materials in a processingsystem including a plurality of processing means processing materialstransported thereto by transporting means, comprising the steps of:loading materials on said transporting means; issuing a material requestfrom any processing means when the processing means requires a material;communicating the material request from the processing means whichissued the material request to other processing means; detectingmaterials transported by said transporting means by using a detectormeans associated with at least one of said processing means and storingthe results of detection; causing each of said processing means tosearch a requested material indicated by the material request, based onthe stored results of detection; reserving said requested material forthe processing means which issued the material request when saidmaterial is found on said transporting means as a result of thesearching step; and unloading said reserved material from saidtransporting means upon arrival of said material at the position of saidprocessing means which issued the material request thereby supplyingsaid material to said processing means. .Iaddend. .Iadd.14. An apparatusfor transportation of materials in a processing system including aplurality of processing means processing materials transported theretoby transporting means, comprising load/unload commanding means forcommanding loading of materials on said transporting means andcommanding unloading of said materials from said transporting means;transmission control means provided for each of said work-processingmeans for transmitting a material request issued from processing meansassociated therewith to other processing means and receiving a materialrequest transmitted from the other processing means; and materialselector means provided for each of said processing means and comprisingmeans for storing the material request issued from the processing meansassociated therewith and the material requests transmitted from theother processing means; means for detecting materials on saidtransporting means and storing the results of detection; means forsearching a requested material based on the contents of said materialrequest storing means and said means for storing the results ofdetection; and means for reserving the requested material when it isfound by said searching means that the requested material on saidtransporting means and reporting a reservation of requested material toother processing means. .Iaddend. .Iadd.15. An apparatus according toclaim 14, wherein each of said processing means comprises a firstsubsystem for carrying out a material process and a second subsystemincluding said material selection means and said transmission controlmeans, said transmission control means being connected through atransmission path to the transmission control means of the otherprocessing means. .Iaddend. .Iadd.16. An apparatus according to claim15, wherein each of said processing means further comprises means forreporting to the load/unload commanding means that requested material isnot reserved after repeated issuance of a material request apredetermined number of times, so as to cause said load/unloadcommanding means to supply the requested material. .Iaddend. .Iadd.17. Amethod for controlling machine tools in a distributed system having aplurality of subsystems, each of which has a machine tool and controllerfor operating an associated machine tool and a transmission mediumconnected with said subsystems for transmitting information to saidsubsystems, comprising the following steps executed by each of saidsubsystems;transmitting the information to said transmission medium;receiving information transmitted from other subsystems through saidtransmission medium; independently determining whether or not themachine tool is operated based on the received information from saidtransmission medium; and operating said machine tool based on theindependently determined result. .Iaddend. .Iadd.18. A method forcontrolling machine tools in a distributed system having a plurality ofsubsystems, each of which has a machine tool for processing at least onematerial and a controller for operating the machine tool, a means forrelatively moving materials with respect to said subsystems and atransmission medium connected with said subsystems for transmittinginformation relating to the materials to said subsystems, comprising thefollowing steps executed by each of said subsystems: transmittinginformation relating to the materials moved by said moving means to saidtransmission medium; receiving information relating to the materialsmoved by said moving means and transmitted from other subsystems throughsaid transmission medium; independently determining whether or not themachine tool is operated for processing the material moved by saidmoving means based on the received information relating to the materialsfrom said transmission medium; and operating the machine tool based onthe independently determined result. .Iaddend. .Iadd.19. A materialselector subsystem, comprising:means for detecting a pallet on aconveyor; a pallet detector for receiving signals from the detectingmeans; a material selector for selectively unloading materials from theconveyor; a material selector controller operatively associated with thematerial selector, including a processor, an interface operativelyassociated with the pallet detector, an interface operatively associatedwith the information transmission controller, a material tracking fileoperatively associated with the processor, a requested material datafile operatively associated with the processor, a pallet monitoringtimer operatively associated with the processor, a material requestmonitoring timer operatively associated with the processor, and aninterface for connecting the subsystem with a materials processor forprocessing a selected one of the materials on the conveyor; and aninformation transmission controller for exchange of information with atleast one other material selector subsystem. .Iaddend. .Iadd.20. Thesubsystem according to claim 19, wherein the material selectorcontroller further comprises an input/output buffer operativelyassociated with the processor for storing data of requested material andtransferring said data to the requested material data file. .Iaddend..Iadd.21. The subsystem according to claim 19, wherein the materialtracking file stores data comprising material name data and a statusdata indicating whether a material has been reserved for anothermaterial selector subsystem. .Iaddend. .Iadd.22. The subsystem accordingto claim 19, wherein the requested material data file comprises materialname data and a status data to be found in the material tracking file tobroadcast from the material selector controller via an informationtransmission log for reserving still unreserved materials. .Iaddend..Iadd.23. A method for manufacturing a product in a distributed systemincluding a plurality of subsystems for transmitting information betweensaid subsystems, said method comprising the following steps executed byeach of said subsystems:transmitting the information to saidtransmitting medium; receiving the information transmitted from othersubsystems through said transmission medium; independently selectingoperation to be performed by its own subsystem based on the receivedinformation from said transmission medium; and executing the selectedoperation based on the result of the selecting step. .Iaddend.